Developmental changes in inspiratory network complexity and burst timing in rat in vivo

Developmental changes in intrinsic membrane properties and synaptic transmission are present within the central respiratory neural network. The influence of maturation on the complex dynamics (i.e., complexity) underlying the central respiratory neural network as well as burst timing, however, remain to be examined. Therefore, we calculated the approximate entropy (ApEn; as an index of network complexity) of inspiratory motor discharges recorded from the diaphragm in spontaneously breathing urethane-anesthetized neonatal rats. Our findings demonstrate that changes in central inspiratory neural network complexity and burst timing occur with maturation, such that in the older neonatal rats, the neural controller exhibits higher ApEn (i.e., less system order) and longer inspiratory bursts. We suggest that these changes not only reflect the developmental reconfiguration of the central respiratory network but also provide quantitative insight into the extent of reconfiguration.